Detergent compositions capable of cleaning and softening fabrics from the same wash liquor are described in GB 1 514 276, EP 120 528B and EP 173 398A (Unilever). These patent specifications describe detergent compositions containing water-insoluble long-chain amines, preferably tertiary amines, that provide wash cycle softening benefits. In the preparation of spray-dried detergent powders these amines may, if desired, be included in the slurry for spray-drying, but this processing method is not preferred because high spray-tower temperatures may lead to degradation of the amines, with an adverse effect on product quality. The preferred method for incorporating a water-insoluble fabric softening amine in spray-dried powders is to liquefy it by melting or solvent dissolution, and either to spray the melt or solution directly onto the spray-dried base powder, or to spray it onto a suitable carrier material which is then dry-mixed with the spray-dried base powder. The carrier material which has hitherto been chosen for this purpose is sodium perborate monohydrate, because this material is a good water-soluble porous carrier and is a normal constituent of heavy duty detergent powders which is always dry-mixed with the spray-dried base powder because of its unsuitability for spray-drying: it thus provides a convenient route for incorporating amines with minimal process disruption. Sodium perborate monohydrate/tertiary amine premixes for addition to detergent powders are commercially available. They provide excellent delivery of the amine and good softening, but suffer from the major disadvantage that they are hazardous to store and handle because of the powerful oxidizing nature of sodium perborate monohydrate. Sodium perborate tetrahydrate is insufficiently porous and insufficiently water-soluble to be used as a carrier material.
CA 1 186 458 (Bristol-Myers) discloses a granular fabric softening composition, for incorporation in detergent powders, comprising a particulate nitrogen-containing compound, for example, a primary, secondary or tertiary amine, having a particle size of less than 420 .mu.m, and an inert adjuvant, for example, borax or sodium sesquicarbonate. Amines are not generally particulate materials--those suitable for fabric softening are liquids or low-melting-point waxy solids at ambient temperature--and it is necessary to convert them. to finely divided particulate form in order to prepare the composition of CA 1 186 458. The inert adjuvant apparently acts as a diluent rather than a carrier.
EP 221 776A (Unilever), published on 13 May 1987, describes and claims novel porous materials suitable for carrying liquid components in detergent compositions. One such material, crystal-growth-modified Burkeite, is prepared by drying (preferably spray-drying) a slurry containing sodium carbonate and sodium sulphate in an appropriate ratio and a crystal growth modifier, added to the slurry not later than the sodium carbonate so as to influence the growth of crystals of the double salt Burkeite. Crystal-growth-modified Burkeite is characterized by a high capacity for taking up liquid detergent components.
We have now discovered that crystal-growth-modified Burkeite and related carbonate-based salts may be used as inert, non-hazardous carriers for liquid or waxy fabric softening amines. Unexpectedly, a Burkeite/amine premix gives more efficient softening than a sodium perborate monohydrate/amine premix containing the same amount of amine.